The purposes of this application are to detail stimulus specific mechanisms of arachidonate metabolism and free radical and lysosomal enzyme release in human and sheep neutrophils (PMNs) and to test the hypothesis that immune vascular injury results from release of oxygen radicals from activated neutrophils adherent to endothelial cells. In vitro studies with PMNs isolated from human and sheep blood will determine activation responses with 4 different stimuli using aggregation, chemotaxis, superoxide anion release, lysosomal enzyme release, and metabolism of endogenous and exogenous arachidonic acid as indices of activation. In addition, detailed studies of changes in neutrophil morphology with each stimulus will be made. In vivo studies using chronically prepared unanesthetized sheep will determine the physiologic responses to the stimuli used to activate PMNs. morphologic studies will also be carried out in the sheep experiments to obtain evidence of PMN endothelial cell interactions. Drug treatment studies will be used to clarify mechanisms of release reactions. For each drug, dose response curves will be constructed for the PMN functions listed above using vehicle treated human and sheep cells as controls. Additional binding studies usingmpure C3a des arg and C5a des arg will be made to test the effects of drugs on anaphylatoxin binding. Similarly, measurements of PMN cAMP concentration will be made in those instances in which treatment alters release reactions. Studies with unanesthetized sheep will compare responses in vehicle treated and drug treated sheep. The results of these experiments will provide much needed data on the interrelationships among release reactions from activated PMNs and on the mechanisms of immune vascular injury. By comparing activation responses and mechanisms of release reactions in human and sheep pMNs, the extent to which measurements made in sheep may be applicable to immune vascular injury in humans will be clarified.